28K - Rear Brakes Shot, Front O.K.?

[bkaiser]

Well, I had some time last night, so I cuddled up with the service manual to see what I could glean from that source. The four wheel ABS trucks do not have a proportioning valve. That function is performed electronically in the ABS unit. Great. One more simple, relatively cheap suspect removed from the equation. Reading into the system description, it appears that it provides a lot of rear bias until the RWAL sensor indicates impending lock up, then shifts the bias forward.



I'm beginning to think I don't work my truck hard enough, and in 'commuting mode' am mostly using the rear brakes. At least I now know to keep a close eye on the rear pads before I trash another set of rotors.

 

[JHardwick]

My rears wore a tad faster than my fronts.

 

[DPKetchum]

Normal. Smaller pads and softer compond.

 

[NDanecker]

It seems odd to have the rear brakes wear more then front. Also never heard of softer material for rear brakes or designing the brakes such that the rear brakes wear before the front. But then again God only knows what the engineers at Dodge had in their heads the day they chose brake compound, rotor & piston/caliper size, etc.



I checked mine when I rotated tires (~44k miles) and they seem to have very little wear with plenty of meat left both front and back! However, I have a 6-speed with e-brake which I use most of the time during hard stops especially from highway speeds.

 

[DPKetchum]

Its NOT DODGE. Its almost all the manufactures and its kinda been this way on four wheel disc set ups for over two decades. Rears don't have the heat the fronts do so a differant compound. Also a smaller pad surface. Front DISC rear DRUM the fronts usually wear faster but NOT on four wheel disc brake setups.

 

[NDanecker]

Its NOT DODGE. Its almost all the manufactures and its kinda been this way on four wheel disc set ups for over two decades. Rears don't have the heat the fronts do so a differant compound. Also a smaller pad surface. Front DISC rear DRUM the fronts usually wear faster but NOT on four wheel disc brake setups.

They use smaller pads (surface area) and smaller diameter rotors because the rears do a smaller percentage of work. If the clamping force, pad area, rotor diameter, etc. were kept the same they'd lock up way before the fronts. The trucks front tires see more downward force as a result of the negative acceleration when stopping (in addition to the poor weight distribution these trucks are prone to). Since the trucks CG is above the plane the tires are on, the truck wants to rotate yielding a moment & increases the load on the front tires. This downward force offers the ability to apply more pressure without the wheels skidding/locking up. While this is happening the downward force applied by the rear tires decrease which is why the tires are able to lock up sooner.



The heat generated is just what happens when you turn kinetic energy into potential. It also decreases performance and not wanted. From what you posted it seems you are implying that heat is good or increases the ability to stop thus the reason for the smaller rear brake setup. I apologize if I misunderstood you.



Now, they can choose a softer compound, smaller brakes, etc. for the rear, but that is only to try and get both tires to lock up at the same time during what they calculate to be a typical stop with a typical load. Many variables here……and thank goodness for ABS!!!



IMO, if the rear brakes are wearing out before the fronts there is something wrong. Either the driver is REALLY taking it easy on the truck which is not likely, the brakes are not setup properly or malfunctioning and/or the engineers didn’t do their homework. Either way, rear brakes wearing out before the fronts (on both 4 wheel disc & front disc/rear drum arrangements) is not common and hasn’t been for the fleet of cars/trucks that I owned.



Again, the above is my opinion and coming from what I learned in the 5 years of Mech Engineering schooling. I do not design brakes on a daily basis so if you’re an automobile engineer and design brakes I’m certainly open to your analysis.

 

[JHardwick]

My rears wore slightly quicker than my fronts.

 

[DPKetchum]

My experiance is from running/managing service depts for 25 or so years. Some with as many as 40 plus techs. Nissan,G. M. (several lines)Isuzu,Mazda and last but not least D. C. . on four wheel disc brake designs rears wore faster. Now as I also think about the rear pad THICKNESS may also be thinner as well as smaller and softer matierial.

 

[mbhw]

Expect 100,000 miles on my original brakes!

I have installed air assisted accumulators on my 04 3500. Had the same ones on my 2000 Ford F250 and transferred them onto my 04 3500. Had over 93000 mi when traded for my 3500. I pull a 18000 lb plus 5th wheel. I could buy 4-5 accumulators for all the brake jobs you have to do.



Got you thinking now I bet. Oo.